The main function of the brain, or nervous system, is to receive inputs from the environment, process that information, and then tell the rest of the body what to do. The brain does this with an extremely complex array of nerve cells (neurons), whose main function is to connect with and talk to other neurons. In order to form these networks of functional connections, neurons must acquire an elaborate structure, including complex branching patterns of axons and dendrites. Thus, identification of the genes that control the acquisition of these elaborate cell shapes is important for understanding how the nervous system develops, and may also provide insights into what goes wrong in disease states of mental health. To identify the genes involved in the morphological differentiation of neurons, we will develop a time-resolved genetic loss-of-function approach that can be used in the zebrafish model organism. By in vivo electroporation of morpholino antisense oligonucleotides, we can knockdown expression of a particular gene at a specific time in development. Through the same method, we can incorporate expression plasmids that code for the green fluorescent protein (GFP), which allows us to use fluorescence microscopy to visualize the changes in cell shape that occur during development in live zebrafish embryos. Thus, we can examine whether a target gene of interest is important for morphological differentiation by examining whether loss-of-function of that gene leads to defects in the changes in cell shape visualized with GFP. The target genes that we are interested in are those that translate the signals received from the complex extracellular environment into a cell biological response resulting in changes in cells shape. The phosphoinositide 3-kinase signaling pathway has been implicated in similar processes. We will examine whether PI3-kinase signaling is required for morphological differentiation of neurons by knocking down expression of the p110 catalytic subunit of the kinase, and then examining whether or not neurons still acquire their distinct shapes. [unreadable] PUBLIC HEALTH RELEVANCE: Identifying the genes that control the development of the vertebrate brain is important for understanding what might be defective in disease states, and for identifying drug targets for therapy. Also, knowing which genes are important for guiding the growth of neurons during development may also provide drug target to be re-activated to facilitate regeneration of the nervous system after damage or disease. This project aims to identify the genes involved in development of the nervous system by selectively deleting specific genes and then visualizing changes in the structure of neurons in the zebrafish model organism. [unreadable] [unreadable] [unreadable]